Datasheet

DS2502-E64
2 of 4
The first 32 bytes of the DS2502-E64’s EPROM memory contain a globally unique 64-bit node address
(EUI-64) and are write-protected. The data structure follows the conventions of UniqueWare devices
using Default Data Structure (Figure 1). This format is also known as UDP (universal data packet) and is
commonly used in 1-Wire APIs. Therefore, if using one of those APIs one can call a high level function
to read and verify the inverted CRC16. The UDP is defined in Application Note 114, 1-Wire File
Structure, and the APIs can be found in the 1-Wire Software Development Kits.
Figure 1. EUI-64 NODE ADDRESS CHIP DATA STRUCTURE
CRC16
COMPANY ID VALUE EXTENSION ID VALUE PROJECT ID
(UNUSED)
MSB LSB MSB LSB MSB LSB MSB LSB
LENGTH
17 BYTES
FFh
2 BYTES
3 BYTES CONSTANT
006035h
5 BYTES SERIALIZATION
4 BYTES CONSTANT
00001128h
1 BYTE
0Ch
HIGH ADDRESS LOW ADDRESS
The data record starts with a length byte (0Ch) and the 4-byte UniqueWare Project ID 00001128h. The
next eight bytes contain the EUI-64 global identifier (node address) which consists of an incrementing
40-bit extension identifier and the IEEE-assigned 24-bit company ID value 006035h. An inverted 16-bit
CRC ends the data record. The remaining bytes of the 32-byte memory page remain unprogrammed.
Neither the 40–bit extension identifier nor the 24-bit company ID are related to the 64-bit ROM
registration number. The ROM registration number is used to provide a unique address to access the
DS2502-E64 when multidropped on a 1-Wire bus.
EXAMPLE
Assume that a manufacturer’s company ID value is 006035h and the 40-bit extension identifier is
234567ABCDh. The EUI-64 value generated from these two numbers is 006035234567ABCDh, whose
byte and bit representations are illustrated in Figure 2.
Figure 2. SAMPLE EUI-64 VALUE
MOST SIGNIFICANTBYTE LEAST SIGNIFICANTBYTE
00 60 35 23 45 67 AB CD HEX
0000 0000 0110 0000 0011 0101 0010 0011 0100 0101 0110 0111 1010 1011 1100 1101 BINARY
MOST SIGNIFICANT BIT LEAST SIGNIFICANT BIT
This information is stored in the DS2502-E64 as 64-bit number with the least significant byte at the lower
address. Including the length byte and the inverted CRC, the complete set of data is shown in Figure 3.
Figure 3. PHYSICAL ADDRESS AND DATA MAPPING INSIDE THE DEVICE
ADDRESS 0E 0D 0C 0B 0A 09 08 07 06 05 04 03 02 01 00
DATA 3E FF 00 60 35 23 45 67 AB CD 00 00 11 28 0C